Acting up how? I just did a pc tune up on mine, as it was acting up yesterday, internet was having fits and what not. But it wasn't a virus, just fragmented disc, and other errors. Have you done a full scan?
EDIT: ninja'ed.
With my anti-virus, yes.
I see that you're paying for Antivirus protection, Microsoft Security Essentials is a great free alternative. And common sense is a good rule of thumb. Avoid questionable websites.
We all slip up every now and then.

Basically my problems began earlier today, when FireFox began locking up for a few moments and not displaying information correctly. I thought nothing of it and ran a full system scan.
Now when I get back World of Warcraft can't connect to it's log-in server, as well the game loads the UI but the game world is solid black.
The reason I am concerned of a virus is that I inadvertently visited such a questionable site earlier today. Thus my concern.
Granted, the two issues are probably unrelated, but it never hurts to double check now does it? The red flag in this situation is that nothing
should have changed between when I first got on earlier until now. Yet something has.